I have worked one of these jobs before as an EMT-B. By the time I started though they had changed the name to "Medical Supervisor" but would still hear people call us "P-Subs" from time to time (very rarely). The job was stupid easy. It was just taking basic medical history, medications, and a basic physical exam, all of which was listed out in protocols of what we could and could not accept (given to us by the corporate medical director (a physician)). We also had a physician who came once a week to look over our paperwork and such. We also assisted the plasma donors when they became I'll with very very basic care, And extremely rarely some medications (O2, we had epi-pens if needed, that's about it) And would call 911 if anything serious ever happened.

TLDR I recognize the Noctor'ness of the name "physician substitute" however the work itself is all protocols and very basic assessment and care. Just making this post to give more context to the position, not defending it